"SIX years ago, Greg Lemke, a scientist in La Jolla, Calif., took a close look at his modest 40-year-old house and realized, he said, ''that the basic structure -- plumbing, drains, wiring, roof, furnace -- was starting to fall apart.'' Mr. Lemke, an architecture buff, figured that while fixing all those things, he should try to turn the ordinary ranch house into something more distinguished".